Electronic devices, such as semiconductor dice and packages, are typically mounted to a substrate, such as a circuit board, mother board or a module substrate. Typically, interconnects on the electronic device are bonded to corresponding electrodes on the substrate. For example, the interconnects can comprise bumped bond pads, or terminal contacts such as metal balls, metallurgically bonded to the electrodes on the substrate. One specific type of bonding developed by IBM is known as C4 (controlled collapse chip connection).
One problem that occurs with this type of mounting is thermal stress caused by the CTE (coefficient of thermal expansion) mismatch between the electronic device and the substrate. Thermal stresses can develop as the electronic device heats up during start up and operation, and then cools down during non-use or steady state operation with a cooling device. For example, the thermal stresses can develop in the bonded connections between the interconnects on the electronic device and the electrodes on the substrate. Thermal stresses and heat build up can adversely affect the performance of the electronic device and can cause joint fatigue.
Most electronic systems, such as computers, have cooling devices, such as fans, designed to dissipate the heat generated by the electronic devices. However, these devices may not run continuously, and may take several seconds after start up to reach full capacity. In some situations, heat may build up in the interconnects generating thermal stresses and heat in the electronic devices. The present disclosure is directed to an interconnect, and to a method for mounting an electronic device to a substrate, designed to substantially eliminate thermal stresses and to reduce heat build up.